REV. 0

AD5303/AD5313/AD5323

–17–

SCLK

SYNC

DIN

DB15

DB0

DB15

DB0

DB15

DB0

SDO

INPUT WORD FOR DAC N

INPUT WORD FOR DAC (N+1)

UNDEFINED

INPUT WORD FOR DAC N

SCLK

SDO

Figure 45. Daisy-Chaining Timing Diagram

Power Supply Bypassing and Grounding

In any circuit where accuracy is important, careful consideration

of the power supply and ground return layout helps to ensure

the rated performance. The printed circuit board on which the

AD5303/AD5313/AD5323 is mounted should be designed so

that the analog and digital sections are separated, and confined

to certain areas of the board. If the AD5303/AD5313/AD5323

is in a system where multiple devices require an AGND to

DGND connection, the connection should be made at one

point only. The star ground point should be established as close

as possible to the AD5303/AD5313/AD5323. The AD5303/

AD5313/AD5323 should have ample supply bypassing of 10

µF

in parallel with 0.1

µF on the supply located as close to the

package as possible, ideally right up against the device. The

10

µF capacitors are the tantalum bead type. The 0.1 µF

capacitor should have low Effective Series Resistance (ESR)

and Effective Series Inductance (ESI), like the common

ceramic types that provide a low impedance path to ground at

high frequencies to handle transient currents due to internal

logic switching.

The power supply lines of the AD5303/AD5313/AD5323 should

use as large a trace as possible to provide low impedance paths

and reduce the effects of glitches on the power supply line. Fast

switching signals such as clocks should be shielded with digital

ground to avoid radiating noise to other parts of the board, and

should never be run near the reference inputs. Avoid crossover

of digital and analog signals. Traces on opposite sides of the

board should run at right angles to each other. This reduces the

effects of feedthrough through the board. A microstrip tech-

nique is by far the best, but not always possible with a double-

sided board. In this technique, the component side of the board

is dedicated to ground plane while signal traces are placed on

the solder side.